Semiconductor device and manufacturing method thereof

ABSTRACT

The reliability of wirings, each of which includes a main conductive film containing copper as a primary component, is improved. On an insulating film including the upper surface of a wiring serving as a lower layer wiring, an insulating film formed of a silicon carbonitride film having excellent barrier properties to copper is formed; on the insulating film, an insulating film formed of a silicon carbide film having excellent adhesiveness to a low dielectric constant material film is formed; on the insulating film, an insulating film formed of a low dielectric constant material as an interlayer insulating film is formed; and thereafter a wiring as an upper layer wiring is formed.

CROSS REFERENCES TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationJP 2003-083348 filed on Mar. 25, 2003, the contents of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a techniquefor manufacturing it and, particularly, to a technique effectivelyapplied to a semiconductor device having wirings each including a mainconductive film containing copper as a primary component.

Elements of the semiconductor device are connected by, for example, amultilayer wiring structure, whereby a circuit is configured. Along withan ultra-fine structure, an embedded wiring structure has been developedas a wiring one. The embedded wiring structure is formed by, forexample, embedding, by use of a Damascene technique (Single-Damascenetechnique and Dual-Damascene technique), wiring materials in wiringopenings such as wiring grooves and holes formed in an insulating film.

Japanese patent Laid-open No. 2002-43419 discloses a technique in whicha 50 nm thick P—SiC film as a Cu atom diffusion preventing layer isformed on a Cu layer as an underlying wiring, and a low dielectricconstant layer as an interlayer insulating film is formed on the P—SiCfilm.

Japanese Patent Laid-open No. 2002-270691 discloses a technique inwhich, after a copper wiring is formed, a 5 to 50 nm thick insulatingbarrier film made of silica carbide (SiC), silica nitride (SiN) and amixture (SiCN) thereof, etc. is formed on a plane formed by a CMPmethod.

Also in Non-patent Document 1, there is described a technique for using,as a barrier dielectric, a two-layer dielectric comprising a lower α-SiCfilm and a upper α-SiCN film.

[Non-patent Document 1]: C. C. Chiang, M. C. Chen, Z. C. Wu, L. J. Li,S. M. Jang, C. H. Yu, M. S. Liang, TDDB Reliability Improvement in CuDamascene by using a Bilayer-Structured PECVD SiC Dielectric Barrier,“2002 IITC (International Interconnect Technology Conference)”, (U.S.A.)IEEE, 2002, pp. 200-202

SUMMARY OF THE INVENTION

Examinations by the present inventors have found that if a semiconductordevice having an embedded copper wiring is left to stand at the hightemperature, the electric resistance of the embedded copper wiring isincreased by stress migration. This degrades the reliability of theembedded copper wiring.

In the semiconductor device having the embedded copper wiring, it isalso required to improve TDDB (Time Dependence on Dielectric Breakdown)life of the embedded copper wiring. According to the examinations by thepresent inventors, it has been found out by TDDB life tests that copperions in the wiring are drifted by an electric field exerted betweenadjacent wirings in the embedded copper wirings disposed on the samelayer, whereby dielectric breakdown is caused.

Accordingly, in the embedded copper wiring, there is a demand forfurther improvement of the reliability, for example, the improvement ofstress migration characteristics and/or the enhancement of TDDB life.

An object of the present invention is to provide a semiconductor deviceand a manufacturing method thereof, which are capable of improving thereliability of the wirings each including a main conductive filmcontaining copper as a primary component.

The above and other objects and novel features will be apparent from thedescription of this specification and the accompanying drawings.

A semiconductor device according to the present invention is oneobtained by using a laminated film of: a first barrier insulating filmformed, as a barrier insulating film of an embedded copper wiring, on aninsulating film in which a copper wiring is embedded, and havingexcellent barrier properties to copper; and a second barrier insulatingfilm formed on the first barrier insulating film and having excellentadhesiveness to a low dielectric constant material film.

Also, a semiconductor device according to the present invention is oneobtained by using a laminated film of: a first barrier insulating film,as a barrier insulating film of an embedded copper wiring, on aninsulating film in which a copper wiring is embedded, and made of amaterial containing silicon and carbon and at least one of nitrogen andoxygen; and a second barrier insulating film formed on the first barrierinsulating film and made of silicon carbide.

Further, a semiconductor device according to the present invention isone in which, in a barrier insulating film of an embedded copper wiring,a concentration of nitrogen in a barrier insulating film near theinterface between a wiring and the barrier insulating film is higherthan that of the barrier insulating film near the interface between alow dielectric constant material film disposed on the barrier insulatingfilm and the barrier insulating film.

Further, a semiconductor device according to the present invention isone in which: an insulating film having a function of restraining orpreventing the diffusion of copper is formed on an insulating film inwhich a copper wiring is embedded; an insulating film having a functionof controlling a stress is formed thereon; the stress of a laminatedfilm of the insulating film having a function of restraining orpreventing the diffusion of copper and the insulating film having afunction of controlling the stress is −180 MPa or more.

Further, a manufacturing method for a semiconductor device according tothe present invention comprises the steps of: forming a first barrierinsulating film having excellent barrier properties to copper, on aninsulating film in which a copper wiring is embedded; forming a secondbarrier insulating film having excellent adhesiveness to a lowdielectric constant material film on the first barrier insulating film;and forming a low dielectric constant material film on the secondbarrier insulating film.

Further, a manufacturing method for a semiconductor device according tothe present invention comprises the steps of: forming a first barrierinsulating film made of a material containing silicon and carbon and atleast one of nitrogen and oxygen, on an insulating film in which acopper wiring is embedded; forming a second barrier insulating film madeof silicon carbide, on the first barrier insulating film; and forming alow dielectric constant material film on the second barrier insulatingfilm.

Further, a manufacturing method for a semiconductor device according tothe present invention comprises the step of: forming a barrierinsulating film, on an insulating film in which a copper wiring isembedded; and forming a low dielectric constant material film on thebarrier insulating film, wherein a concentration of nitrogen in thebarrier insulating film near the interface between a wiring and thebarrier insulating film is higher than that of the barrier insulatingfilm near the interface between a low dielectric constant material filmdisposed on the barrier insulating film and the barrier insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anembodiment of the present invention.

FIG. 2 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 1.

FIG. 3 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 2.

FIG. 4 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 3.

FIG. 5 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 4.

FIG. 6 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 5.

FIG. 7 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 6.

FIG. 8 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 7.

FIG. 9 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 8.

FIG. 10 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 9.

FIG. 11 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 10.

FIG. 12 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 11.

FIG. 13 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 12.

FIG. 14 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process of another embodiment.

FIG. 15 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 13.

FIG. 16 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 15.

FIG. 17 is a graph showing the results of TDDB life tests of embeddedcopper wirings.

FIG. 18 is a graph showing resistance-rising ratios obtained after testsin which embedded copper wirings are left to stand at a hightemperature.

FIG. 19 is a graph showing resistance-rising ratios obtained after testsin which embedded copper wirings are left to stand at a hightemperature.

FIG. 20 is a graph showing resistance-rising ratios obtained after testsin which embedded copper wirings are left to stand at a hightemperature.

FIG. 21 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 22 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 21.

FIG. 23 is a graph showing a concentration distribution of nitrogen (N)in a thickness direction of an insulating film.

FIG. 24 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 22.

FIG. 25 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 24.

FIG. 26 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 27 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 26.

FIG. 28 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 27.

FIG. 29 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 28.

FIG. 30 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 29.

FIG. 31 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 30.

FIG. 32 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 31.

FIG. 33 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 34 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 33.

FIG. 35 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 34.

FIG. 36 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 35.

FIG. 37 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 36.

FIG. 38 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 37.

FIG. 39 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 38.

FIG. 40 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 39.

FIG. 41 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 40.

FIG. 42 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 41.

FIG. 43 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 44 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 43.

FIG. 45 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 44.

FIG. 46 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 45.

FIG. 47 is a sectional view showing the principal portion of asemiconductor device according to another embodiment of the presentinvention.

FIG. 48 is a graph showing a stress of a laminating film.

FIG. 49 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 50 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 49

FIG. 51 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 50.

FIG. 52 is a sectional view showing the principal portion of asemiconductor device in a manufacturing process according to anotherembodiment of the present invention.

FIG. 53 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 52.

FIG. 54 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 53.

FIG. 55 is a sectional view showing the principal portion of thesemiconductor device in the manufacturing process following FIG. 54.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail based on the drawings. Note that, through all the drawings fordescribing the embodiments, members having the same function are denotedby the same reference symbol and the repetitive description thereof willbe omitted. Further, in the below-mentioned embodiments, the descriptionof an identical or similar section(s) will not be repeated in principleunless required especially.

First Embodiment

A semiconductor device and a manufacturing process thereof according toa first embodiment of the present invention will be explained inreference to the drawings. FIG. 1 is a sectional view of the principalportion of the semiconductor device, for example, a MISFET (MetalInsulator Semiconductor Field Effect Transistor) in the manufacturingprocess according to the first embodiment of the present invention.

As shown in FIG. 1, for example, on a main surface of a semiconductorsubstrate (semiconductor wafer) 1 made of a p-type single crystalsilicon and the like and having a specific resistance of approximately 1to 10 Ωcm, an device isolation region 2 is formed. The device isolationregion 2 is made of silicon oxide or the like and is formed by, forexample, a STI (shallow Trench Isolation) or LOCOS (Local Oxidization ofSilicon) method or the like.

Next, a p-type well 3 is formed in an area for forming an n-channel typeMISFET on the semiconductor substrate 1. The p-type well 3 is formed byan iron-implantation of impurities, for example, boron (B) and the like.

Then, a gate insulating film 4 is formed on a surface of the p-type well3. The gate insulating film 4 is formed of, for example, a thin siliconoxide film or the like and is formed by, for example, a heat oxidizationmethod or the like.

Next, a gate electrode 5 is formed on the gate insulating film 4 of thep-type well 3. For example, a poly crystal silicon film is formed overthe semiconductor substrate 1, and phosphorous (P) or the like ision-implanted into the poly crystal silicon film to make a lowresistance n-type semiconductor film, and the poly crystal silicon filmis dry etched and patterned, whereby the gate electrode 5 formed of thepoly crystal silicon film can be formed.

Next, impurities such as phosphorous are ion-implanted into areasdisposed on both sides of the gate electrode 5 of the p-type well 3, andthereby an n-type semiconductor region 6 is formed.

Next, on a side wall of the gate electrode 5, a sidewall spacer orsidewall 7 made of, for example, silicon oxide or so is formed. Thesidewall 7 is formed by, for example, depositing a silicon oxide filmover the semiconductor substrate 1 and anisotropically etching thissilicon oxide film.

After the sidewall 7 is formed, an n⁺ type semiconductor region 8(source and drain) is formed by, for example, ion-implanting impuritiessuch as phosphorous into the areas disposed on both sides of the gateelectrode 5 and the sidewall 7 of the p-type well 3. The impurityconcentration of the n⁺ type semiconductor region 8 is higher than thatof the n⁻ type semiconductor region 6.

Next, by exposing the surfaces of the gate electrode 5 and the n⁺ typesemiconductor region 8 and, for example, depositing a cobalt (Co) filmthereon to perform a thermal treatment, silicide films 5 a and 8 a areformed on the surfaces of the gate electrode 5 and the n⁺ typesemiconductor region 8, respectively. Thereby, a diffusion resistanceand a contact resistance of the n⁺ type semiconductor region 8 can bemade low. Thereafter, the non-reactive cobalt film is removed.

In this manner, an n-channel type MISFET (Metal Insulator SemiconductorField Effect Transistor) 9 is formed on the p-type well 3.

Next, an insulating film 10 made of silicon nitride or the like, and aninsulating film 11 made of silicon oxide or the like are laminated inthis order onto the semiconductor substrate 1. Then, the insulatingfilms 11 and 10 are dry etched sequentially, whereby contact holes 12are formed over tops or the like of the n⁺ type semiconductor region(source and drain) 8. At each bottom of the contact holes 12, part ofthe main surface of the semiconductor substrate 1, for example, part ofthe n⁺ type semiconductor region 8 and part of the gate electrode 5,etc. is exposed.

Next, in the contact holes 12, plugs 13 each made of tungsten (W) or thelike are formed. For example, the plugs 13 may be formed by: forming atitanium nitride film 13 a as a barrier film on the insulating film 11and inside the contact holes 12; thereafter forming a tungsten film onthe titanium nitride film 13 a by a CVD (Chemical Vapor Deposition)method or the like to fill the contact holes 12; and removing theunnecessary tungsten film and titanium nitride film 13 a disposed on theinsulating film 11 by a CMP (Chemical Mechanical Polishing) method oretch back method or the like.

FIGS. 2 to 13 each show a sectional view of the principal portion of thesemiconductor device in the manufacturing process following FIG. 1. Notethat, for an easy understanding, the portions corresponding to thestructure illustrated below the insulating film 11 in FIG. 1 will beomitted in FIGS. 2 to 13.

As shown in FIG. 2, an insulating film (etching stopper film) 14 isformed on the insulating film 11 in which the plugs 13 are embedded. Theinsulating film 14 consists of, for example, a silicon carbide (SiC)film. As another material of the insulating film 14, a silicon nitride(Si_(x)N_(y)) film or the like may be used. The insulating film 14 maybe structured by a laminated film of a silicon carbide (SiC) film and asilicon nitride (Si_(x)N_(y)) film. The insulating film 14 is formed forpreventing damage to the lower layer thereof and deterioration ofdimensional precision for the processing, which are caused due to toomuch removal in forming grooves or holes for wiring formation on anupper insulating film (interlayer insulating film) 15 thereof by theetching. Namely, the insulating film 14 can function as an etchingstopper in etching the insulating film (interlayer insulating film) 15.

Next, the insulating film (interlayer insulating film) 15 is formed onthe insulating film 14. It is preferred that the insulating film 15 ismade of a low dielectric constant material (so-called Low-K insulatingfilm, Low-K material) such as organic polymer or organic silica glass.Note that the low dielectric constant insulating film (Low-K insulatingfilm) means an insulating one having a lower dielectric constant thanthat of a silicon dioxide film included in a passivation film (forexample, TEOS (Tetraethoxysilane) oxide film) by way of an example.Generally, the TEOS oxide film whose specific dielectric constant ∈ isapproximately 4.1 to 4.2 and a film whose dielectric constant is lessthan 4.1 to 4.2 is called a low dielectric constant insulating film.

The organic polymer as the above-mentioned low dielectric constantmaterial includes, for example, SiLK (manufactured by Dow Chemical Co.,USA, specific dielectric constant=2.7, heat resistance temperature=490°C. or higher, dielectric breakdown resistance=4.0 to 5.0 MV/Vm), orFLARE of a poly allyl ether (PAE) system material (manufactured byHoneywell Electronic Materials, specific dielectric constant=2.8, heatresistance temperature 400° C. or higher). This PAE system material hasthe advantages of high basic performance, of excellent mechanicalstrength and thermal stability and low costs. The organic silica glass(SiOC system material) as the above-mentioned low dielectric constantmaterial includes, for example, HSG-R7 (manufactured by HitachiChemicals Co., Ltd., specific dielectric constant=2.8, heat resistancetemperature=650° C.), Black Diamond (manufactured by Applied Materials,Inc., USA, specific dielectric constant=3.0 to 2.4, heat resistancetemperature=450° C.), or p-MTES (manufactured by Hitachi, specificdielectric constant=3.2). The other SiOC system material includes, forexample, CORAL (manufactured by Novellus Systems, Inc., USA, specificdielectric constant=2.7 to 2.4, heat resistance temperature=500° C.),and Aurora 2.7 (manufactured by Nihon ASM Co., Ltd., specific dielectricconstant=2.7, heat resistance temperature=450° C.).

For example, FSG (SiOF system materials); HSQ (hydrogen silsesquioxane)system materials; MSQ (methyl silsesquixane) system material, porous HSQsystem material, porous MSQ material; or porous organic system materialsmay be used as the above-mentioned low dielectric constant material. Theabove-mentioned HSQ system material includes, for example, OCD T-12(manufactured by Tokyo Applied Industry, specific dielectricconstant=3.4 to 2.9, heat resistance temperature=450° C.); FOx(manufactured by Dow Corning Corp., USA, specific dielectricconstant=2.9); OCL T-32 (manufactured by Tokyo Applied Industry,specific dielectric constant=2.5, heat resistance temperature=450° C.)or the like. The above-mentioned MSQ system material includes, forexample, OCD T-9 (manufactured by Tokyo Applied Industry, specificdielectric constant=2.7, heat resistance temperature=600° C.); LKD-T200(manufactured by JSR, specific dielectric constant=2.7 to 2.5, heatresistance temperature=450° C.); HOSP (manufactured by HoneywellElectronic Materials, USA, specific dielectric constant=2.5, heatresistance temperature=550° C.); HSG-RZ25 (manufactured by HitachiChemicals, Co., Ltd., specific dielectric constant=2.5, heat resistancetemperature=650° C.); OCL T-31 (manufactured by Tokyo Applied Industry,specific dielectric constant=2.3, heat resistance temperature=500° C.);LKD-T400 (manufactured by JSR, specific dielectric constant=2.2 to 2,heat resistance temperature=450° C.); or the like. The above-mentionedporous HSQ system material includes, for example, XLK (manufactured byDow Corning Corp., USA, specific dielectric constant=2.5 to 2); OCL T-72(manufactured by Tokyo Applied Industry, specific dielectricconstant=2.2 to 1.9, heat resistance temperature=450° C.); Nanoglass(manufactured by Honeywell Electronic Materials, USA, specificdielectric constant=2.2 to 1.8, heat resistance temperature=500° C. orhigher); or MesoELK (manufactured by Air Products and Chemicals, Inc.,USA, specific dielectric constant=2 or less). The above-mentioned porousMSQ system material includes, for example, HSG-6211X (manufactured byMitachi Chemicals, Co., Ltd., specific dielectric constant=2.4, heatresistance temperature=650° C.); ALCAP-S (manufactured by AsahiChemicals, Co., Ltd., specific dielectric constant=2.3 to 1.8, heatresistance temperature=450° C.); OCL T-77 (manufactured by Tokyo AppliedIndustry, specific dielectric constant=2.2 to 1.9, heat resistancetemperature=600° C.); HSG-6210X (manufactured by Hitachi Chemicals, Co.,Ltd., specific dielectric constant=2.1, heat resistance temperature=650°C.); silica aero gel (manufactured by Kobe Steels, specific dielectricconstart=1.4 to 1.1) or the like. The above-mentioned porous organicsystem material includes, for example, PolyELK (manufactured by AirProducts and Chemicals, Inc., USA, specific dielectric constant=2 orless, heat resistance temperature=490° C.) or the like. Theabove-referenced SiOC system material and SiOF system material areformed by, for example, the CVD method. For example, the above-describedBlack Diamond is formed by the CVD method using a mixture gas oftrimethylsilane and oxygen, or the like. Further, the above-mentionedp-MTES is formed by, for example, the CVD method using a mixture gas ofmethyltrietxysilane and N₂O, or the like. Low dielectric constantinsulating materials except the above-mentioned ones are formed by, forexample, a coating method.

On the insulating film 15 made of such Low-K materials, an insulatingfilm 16 is formed by, for example, the CVD method or the like. Theinsulating film 16 consists of, for example, a silicon oxide (SiO_(x))film represented by silicon dioxide (SiO₂). As another material of theinsulating film 16, a silicon oxynitride (SiON) film may also be used.Additionally, the insulating film 16 can have functions of securing themechanical strength, protecting the surface, and securing humidityresistance, etc. of the insulating film 15 in, for example, processingthe CMP. Further, when the insulating film 15 consists of a siliconoxide (SiOF) film containing fluoride (F), the insulating film 16 mayfunction to prevent the diffusion of fluoride in the insulating film 15.Furthermore, if the insulating film 15 has resistance properties in, forexample, the CMP processing, the formation of the insulating film 16 maybe omitted.

Next, as shown in FIG. 3, by use of a photolithography method and a dryetching method, the insulating films 16, 15, and 14 are selectivelyremoved to form openings (wiring openings and wiring grooves) 17. Atthis time, on the bottom of the opening 17, an upper surface of the plug13 is exposed. Then, a not shown photoresist pattern used as an etchingmask (and a reflection prevention film) is removed by ashing or thelike. If the insulating film 15 is made of a material to be damaged byoxygen plasma, such as an organic polymer system material (for example,the above-mentioned SiLK) and a porous organic system material (forexample, the above-mentioned PolyELK), then the photoresist pattern (andthe reflection prevention film) may be removed by the ashing while theinsulating film 15 is etched by a reducing plasma treatment such as aNH₃ or N₂/H₂ plasma treatment.

Next, as shown in FIG. 4, a relatively thin conductive barrier film 18,for example, having a thickness of approximately 50 nm and made oftitanium nitride (TiN) or the like, is formed on the entirety of themain surface of the semiconductor substrate 1 (namely, on the insulatingfilm 16 including the bottoms and side walls of the openings 17). Theconductive barrier film 18 can be formed by the use of, for example, aspattering or CVD method or the like. The conductive barrier film 18 hasa function of restraining or preventing the diffusion of copper forforming a main conductive film to be mentioned later and a function ofimproving the wettability of copper at the time of reflow of the mainconductive film. As the material of such a conductive barrier film 18,refractory metal nitride such as tungsten nitride (WN) hardly reactingwith copper or tantalum nitride (TaN) may be used instead of titaniumnitride. Further, as the material of the conductive barrier film 18, amaterial obtained by adding silicon (Si) to refractory metal nitride,and a refractory metal such as tantalum (Ta), titanium (Ti), tungsten(W), and a titanium tungsten (TiW) alloy which hardly react with coppermay be used. Additionally, the conductive barrier film 18 may be formedby the use of not only a single film made of the above-mentionedmaterial but also a laminated film.

Next, on the conductive barrier film 18, a main conductive film 19, forexample, having a thickness of approximately 800 to 1600 nm and made ofrelatively thick copper, is formed. The main conductive film 19 may beformed by use of, for example, a CVD, spattering or plating method.Also, the main conductive film 19 may be formed by a conductive filmcontaining copper as a primary component, for example, copper or acopper alloy (containing Cu as a primary component and containing, forexample, Mg, Ag, Pd, Ti, Ta, Al, Nb, Zr or Zn, etc.). Furthermore, aseed film made of relatively thin copper (or a copper alloy) is formedon the conductive barrier film 18 by the spattering method or the like,and thereafter the main conductive film 19 made of relatively thickcopper (or copper alloy) or the like may be formed on the seed film bythe spattering method or the like. Then, a heat treatment is performedto the semiconductor substrate 1 in a non-oxidation atmosphere (forexample, hydrogen atmosphere) at, for example, approximately 475° C.,and thereby the reflow of the main conductive film 19 is carried out andthe insides of the openings 17 are filled with copper without gapstherebetween.

Next, as shown in FIG. 5, the main conductive film 19 and the conductivebarrier film 18 are polished by, for example, the CMP method until theupper surface of the insulating film 16 is exposed. The unnecessaryconductive barrier film 18 and main conductive film 19 on the insulatingfilm 16 are removed, and the conductive barrier film 18 and the mainconductive film 19 are left in the opening 17 serving as a wiringopening, whereby, as shown in FIG. 5, a wiring (first layer wirings) 20consisting of the relatively thin conductive barrier film 18 and therelatively thick main conductive film 19 is formed in the opening 17.The formed wirings 20 are electrically connected through the plugs 13 tothe n⁺ type semiconductor region (source and drain) 8 and the gateelectrode 5. Or, by the etching (electrolysis etching or the like), theunnecessary conductive barrier film 18 and main conductive film 19 maybe removed.

Next, the semiconductor substrate 1 is put in a processing room of aplasma CVD apparatus and an ammonia gas is introduced to apply plasmapower source thereto, and thereafter an ammonia (NH₃) plasma treatmentis performed to the semiconductor substrate 1 (especially, a CMP surfacewhere the wirings 20 are exposed). Or, N₂ gas and H₂ gas are introducedand a N₂/H₂ plasma treatment is performed. By such a reducing plasmatreatment, copper oxide (CuO, Cu₂O, CuO₂) in the surface of the copperwiring oxidized by the CMP is reduced to copper (Cu), and further acopper nitride (CuN) layer is formed on the surface (extremely thinarea) of the wiring 20.

Then, after cleaning is performed as occasion demands, as shown in FIG.6, an insulating film 21 and an insulating film 22 are formed in thisorder by, for example, a plasma CVD method or the like, over theentirety of the main surface of the semiconductor substrate 1,respectively. Namely, the insulating films 21 and 22 are formed in thisorder on the insulating film 16 including the upper surfaces of thewirings 20.

The insulating film 21 functions as a barrier insulating film for copperwiring. Therefore, the insulating film 21 restrains or prevents copperin the main conductive film 19 of the wiring 20 from diffusing in aninsulating film (interlayer insulating film) 23 to be formed later. Theinsulating film 21 is preferably formed of a material film havingexcellent barrier properties to copper (having a high function ofrestraining or preventing copper from diffusing), for example, of asilicon carbonitride (SiCN) film. The silicon carbonitride (SiCN) filmas the insulating film 21 can be formed by, for example, the plasma CVDmethod using a trimethylsilane gas and an ammonia gas. The siliconcarbonitride (SiCN) film has excellent barrier properties to copper andhas a low leak current and good breakdown property accordingly.Therefore, it is possible to securely prevent the diffusion of copper inthe main conductive film 19 of the wiring 20.

In the present embodiment, the insulating film 22 is formed on theinsulating film 21. As shown in FIG. 7, the insulating film 22 ispreferably formed of a material film having excellent adhesiveness to aninsulating film (low dielectric constant material film) 23 to be formedon the insulating film 22, for example, of a silicon carbide (SiC) film.That is, the insulating film 22 functions as an adhesive layer. Thesilicon carbide (SiC) film as the insulating film 22 can be formed by,for example, the plasma CVD method using a trimethylsilane gas. For thisreason, since the insulating films 21 and 22 can be formed by changing,from one to the other of them, a stream of a film-forming gas in thesame plasma CVD film-forming apparatus, the steps of manufacturingprocess can be reduced. The insulating film 22 (SiC) also has barrierproperties to copper (Cu), but is smaller in the effects of the barrierproperties than the insulating film 21 (SiCN). Namely, in the presentembodiment, the insulating film 21 is larger in the barrier propertiesto copper than the insulating film 22. Further, the adhesiveness(adhesion properties) between the insulating film 22 and the insulatingfilm (low dielectric constant material film) 23 is larger than thatbetween the insulating films 21 and 23 at the time when the insulatingfilm 23 is formed on the insulating film 21.

Hereinafter, in the present embodiment, these insulating films 21 and 22may be referred to as first and second barrier insulating films forconvenience in some cases.

If the insulating film 22 is formed of a silicon carbide (SiC) film notcontaining nitrogen and carbon, it is possible to improve theadhesiveness (adhesion properties) between the insulating film 22 andthe below-mentioned insulating film 23. Further, because the insulatingfilm 22 also has barrier properties to copper (function of restrainingor preventing copper from diffusing), it is possible to securelyprevent, by forming the insulating film 22 on the insulating film 21,copper in the main conductive film 19 of the wiring 20 from diffusing.Additionally, of the insulating films 21 and 22, if the insulating film21 contacting to the wiring 20 is formed by a material film havingexcellent barrier properties to copper (for example, by a siliconcarbonitride (SiCN) film) and if the insulation film 22 is formedbetween the insulating films 21 and 23 by a material film havingexcellent adhesiveness (adhesion properties) to the insulating film 23serving as an interlayer insulating film (for example, by a siliconcarbide (SiC) film) even when the material film has slightly lowerbarrier properties to cupper than those of the insulating film 21, thenit is possible to securely prevent copper in the main conductive film 19of the wiring 20 from diffusing and to more properly improve theadhesiveness between the films (insulating films). Therefore, theinsulating film 21 (first barrier insulating film) and the insulatingfilm 22 (second barrier insulating film) are laminated to form theinsulating film 21 on a side of the wiring 20 and the insulating film 22on a side of the insulating film 23, so that the reliability of thewirings can be improved.

Further, it is preferred that the thickness of the insulating film 21 asthe underlying barrier insulating film (first barrier insulating film)is larger than that of the insulating film 22 as the upper barrierinsulating film (second barrier insulating film). The thickness of theinsulating film 21 whose barrier properties to copper are relativelylarge (or whose breakdown property is relatively high) is larger thanthat of the insulating film 22. Therefore, it is possible to enhance thefunction of preventing copper in the main conductive film 19 of thewiring 20 from diffusing and further enhance the breakdown property ofthe entirety of the laminated film consisting of the insulating films 21and 22. Additionally, the thickness of the insulating film 21 ispreferably 40 nm or less, more preferably, for example, approximately 25to 30 nm. Thereby, it is possible to secure high barrier properties tocopper and reduce the capacity between the wirings. Furthermore, thethickness of the insulating film 22 is preferably 10 nm or less, morepreferably, for example, approximately 5 to 10 nm. Accordingly, it ispossible to secure the adhesiveness between the insulating films 22 and23 and reduce the capacity between the wirings.

Further, by using, as the insulating film 21, the above-mentionedsilicon carbonitride (SiCN) film having excellent barrier properties tocopper and good breakdown property, it is possible to more properlyprevent diffusion of copper in the main conductive film 19 of the wiring20 and improve the reliability of the wirings.

Further, as another aspect, as a material of the insulating film 21, afilm (SiCON film) in which oxygen is added to silicon carbonitride(SiCN) or a film (SiOC film) in which oxygen (O) is added to siliconcarbide (SiC) or the like may be used. For this reason, since thedielectric constant of the insulating film 21 can be made small, thecapacity between the wirings can be reduced. Additionally, the leakcurrent between the wirings can be further reduced. Accordingly, as thematerial of the insulating film 21, a material containing silicon andcarbon as well as at least one of nitrogen and oxygen may be used. If asilicon carbonitride (SiCN) film is used as the insulating film 21, itis possible to further enhance the function of preventing the diffusionof copper and improving the breakdown property of the wirings.Meanwhile, if a film (SiCON film) in which oxygen (O) is added tosilicon carbonitride (SiCN) or a film (SiOC film) in which oxygen (O) isadded to silicon carbide (SiC) are used as the insulation film 21, it ispossible to further reduce the capacity between the wirings and also theleakage current.

Next, as shown in FIG. 7, on the insulating film 22, an insulating film(interlayer insulating film) 23, an insulating film (etching stopperfilm) 24, an insulating film (interlayer insulating film) 25, aninsulating film (CMP protective film) 26, and an insulating film (hardmask layer) 27 are formed in this order. The insulating film (interlayerinsulating film) 23 may be made of the same material (low dielectricconstant material) as that of the above-mentioned insulating film 15,and may be formed by the coating method or CVD method or the like. Theinsulating film (etching stopper film) 24 may be made of the samematerial (for example, silicon oxide film) as those of theabove-mentioned insulating film 16. The insulating film (interlayerinsulating film) 25 may be made of the same material (low dielectricconstant materials) as that of the above-descried insulating film 15,and may be formed by the coating method or CVD method or the like. Theinsulating film (CMP protective film) 26 may be made of the samematerial (for example, silicon oxide film) as that of theabove-mentioned insulating film 16. The insulating film 26 can havefunctions of, for example, securing the mechanical strength, protectingthe surface, and securing the humidity resistance, etc. of theinsulating film 25 in the CMP treatment. However, if the insulating film25 has the endurance for, for example, the CMP treatment, the formationof the insulating film 26 may be omitted. The insulating film (hard masklayer) 27 may be formed of, for example, a silicon nitride film (SiN), asilicon carbide (SiC) film, a silicon carbonitride (SiCN) film, or analuminum oxide (AlO) film.

The insulating film 23 is made of the above-mentioned low dielectricconstant material. However, when the above-described low dielectricconstant material film is formed on a material film (corresponding tothe insulating film 21) including nitrogen (N) or oxygen (O) such as thematerial film in which nitrogen (N) or oxygen (O) is added to, forexample, silicon carbide (SiC) (for example, SiCN film, SiOC film, orSiCON film), there is a possibility that the adhesiveness (adhesionproperties) between the underlying film (material film includingnitrogen (N) or oxygen (O)) and the low dielectric constant materialfilm will be reduced. For this reason, there is a possibility that thepeeling will be caused between the films and that if the peelingespecially occurs near the bottom of a via connecting an upper layerwiring and a lower layer wiring, there is a possibility that thereliability of the wirings will be degraded. Such a phenomenon can begenerally caused in the above-mentioned low dielectric constantmaterials, and the occurrence thereof is especially prominent in thecase of using a material containing silicon (Si), oxygen (O), and carbon(C) as the low dielectric constant material, and is more prominent inthe case of using, for example, carbonated silicon (organic siliconglass, SiOC system material, for example, above-mentioned Black Diamondand the like), MSQ (methyl silsesquioxane) system material, or HSQ(hydrogen silsesquioxane) system material (including their porousmaterials) as the low dielectric constant material.

In the present embodiment, since the insulating film 23 made of the lowdielectric constant materials is formed on the insulating film 22 madeof a silicon carbide (SiC) film not including nitrogen (N) or oxygen(O), the adhesiveness (adhesion properties) between the underlyinginsulating film 22 and the insulating film 23 made of the low dielectricconstant materials can be improved. As a consequence, even when the lowdielectric constant materials, especially low dielectric constantmaterials including silicon (Si), oxygen (O) and carbon (C), are used asthe materials of the insulating film 23, it is possible to prevent theinsulating film 23 from peeling off the underlying layer (insulatingfilm 22). Therefore, the reliability of the wirings can be improved.

Next, as shown in FIG. 8, a photoresist pattern 28 is formed on theinsulating film 27 by use of a photolithography method. Then, as shownin FIG. 9, by using the photoresist pattern 28 as an etching mask, theinsulating film 27 is dry etched. Thereby, openings 29 are formed in theinsulating film 27. The opening 29 is formed in the area where a wiringgroove is to be formed. Thereafter, the photoresist pattern 28 isremoved.

Next, as shown in FIG. 10, a photoresist film is formed on theinsulating film 27 so as to fill the openings 29 therewith, and thephotoresist film is exposed, developed and patterned, and thereby aphotoresist pattern 30 is formed. Then, by using the photoresist pattern30 as an etching mask, the insulating films 26, 25, 24, and 23 are dryetched. Thereby, an opening 31 is formed in the insulating films 23 to26. The opening 31 is formed in the area where a via (hole) is to beformed. Therefore, a plane area of the opening 31 is included in that ofthe opening 29. Further, by making the insulating film 22 (and theinsulating film 21) function as an etching stopper film at the time ofthe dry etching, the insulating films 22 and 21 are left on the bottomof the opening 31 so that the upper surface of the wiring 20 cannot beexposed. Thereby, it is possible to prevent the formation of a naturaloxide film on the wirings 20. Also, by the dry etching, it is possibleto prevent copper in the main conductive film 19 of the wiring 20 fromflying in all directions. Thereafter, the photoresist pattern 30 isremoved.

Next, as shown in FIG. 11, by using the insulating film 27 as an etchingmask (hard mask), the insulating films 26 and 25 are dry etched.Thereby, the openings 29 are formed in the insulating films 24 to 27.Since the insulating films 21 and 22 exist (remain) at the bottom of theopening 31 at the time of the etching, the wiring 20 can be preventedfrom being etched.

Next, as shown in FIG. 12, the insulating film 24 is removed at thebottom of the opening 29 by the dry etching, and the insulating films 22and 21 are removed at the bottom of the opening 31 by the dry etching.Thereby, the upper surface of the wiring 20 is exposed from the bottomof the opening 31. Then, the insulating film 27 is removed by the dryetching. The insulating film 27 can be removed by the same dry etchingas that in the step of removing the insulating films 22 and 21 at thebottom of the opening 31, or by another dry etching different therefrom.The insulating film 26 left after removing the insulating film 27 canfunction as a protective film or the like in the CMP treatment.

Next, copper oxide formed on the surface of the wiring 20 (lower copperwiring) exposed from the bottom of the opening 31 is removed, and acleaning treatment of the exposed upper surface of the wiring 20 isperformed. This cleaning treatment can be performed by reducing, intocopper (Cu), copper oxide (CuO, Cu₂O, CuO₂) on the surface of the copperwiring using a reducing plasma treatment such as a hydrogen (H₂) plasmatreatment.

Next, as shown in FIG. 13, on the insulating film 26 including thebottoms and side surfaces of the openings 29 and 31, a conductivebarrier film 32 made of the same material as that of the conductivebarrier film 18 is formed by using the same manner. Then, on theconductive barrier film 32, a main conductive film 33 made of the samematerial as that of the main conductive film 19 is formed by using thesame manner so as to fill the insides of the openings 29 and 31therewith, and the main conductive film 33 and the conductive barrierfilm 32 are polished by, for example, the CMP method until the uppersurface of the insulating film 26 is exposed. The unnecessary conductivebarrier film 32 and main conductive film 33 on the insulating film 26are removed, and the conductive barrier film 32 and the main conductivefilm 33 are left in the openings 29 and 31 serving as wiring openings,and thereby, as shown in FIG. 13, wirings (second layer wirings) 34consisting of the relatively thin conductive barrier film 32 and therelatively thick main conductive film 33 are formed in the openings 29and 31. A portion of the wiring comprising the conductive barrier film32 and the main conductive film 33 embedded in the opening (wiringgroove) 29 is electrically connected to the wiring 20 serving as a lowerlayer wiring, through a via portion consisting of the conductive barrierfilm 32 and the main conductive film 33 embedded in the opening (via)31.

In the present embodiment, on the insulating films 15, 23, and 25 madeof the low dielectric constant materials, the insulating films 16, 24,and 26 made of silicon oxide (or silicon oxynitride) and the like areformed. As another aspect, for example, if the insulating films 15, 23,and 25 are made of the low dielectric materials that can be damaged byan oxygen plasma, a thin insulating film, for example, a silicon carbide(SiC) film is formed on the insulating films 15, 23, and 25 withoutusing an oxidizing plasma such as an oxygen (O₂) plasma and thereby theinsulating films 16, 24, and 26 are formed thereon. FIG. 14 is asectional view showing the principal portion of a semiconductor devicein the manufacturing process according to another embodiment, andcorresponds to FIG. 13. In FIG. 14, on the insulating films 15, 23, and25 made of the low dielectric constant materials, insulating films 16 a,24 a, and 26 a each formed of a thin insulating film formed withoutusing the oxidizing plasma such as the oxygen (O₂) plasma, for example,of a silicon carbide (SiC) film are formed, and thereby the insulatingfilms 16, 24, and 26 made of silicon oxide (or silicon oxynitride) andthe like are formed on the insulating films 16 a, 24 a, and 26 a.Therefore, it is possible to prevent damages (deterioration in quality)of the insulating films 15, 23, and 25 and improve adhesiveness betweenthe insulating films 15, 23, and 25 and the insulating films 16, 24, and26.

FIGS. 15 and 16 show sectional views showing the principal portion ofthe semiconductor device in the manufacturing process following FIG. 13.Note that also in FIGS. 15 and 16, the portions corresponding to thestructure illustrated below the insulating film 11 in FIG. 1 will beomitted.

After obtaining the structure shown in FIG. 13, the semiconductorsubstrate 1 is put in the processing room of the plasma CVD apparatus,and an ammonia gas is introduced and plasma power source is supplied,and then the ammonia (NH₃) plasma treatment is performed to thesemiconductor substrate 1 (especially the CMP surface where the wirings34 are exposed). Or, a N₂ and H₂ gas is introduced to perform a N₂/H₂plasma treatment. By such a reducing plasma treatment, oxide copper(CuO, Cu₂O, CuO₂) of the copper wiring surface oxided by the CMP isreduced to copper (Cu), and further a copper nitride (CuN) layer isformed on the surface (extremely thin area) of the wiring 20.

Then, after the cleaning is performed as occasion demands, as shown inFIG. 15, over the entirety of the main surface of the semiconductorsubstrate 1, an insulating film (first barrier insulating film) 35 andan insulating film (second barrier insulating film) 36 made of the samematerials as and having the same functions as those of theabove-mentioned insulating films 21 and 22 are formed in this order byusing the same manners. Namely, on the insulating film 26 including theupper surfaces of the wirings 34, the insulating films 35 and 36 areformed in this order. Thereby, it is possible to adequately prevent thediffusion of copper in the main conductive film 33 of the wiring 34 andimprove the adhesiveness to an insulating film 37 (interlayer insulatingfilm, low dielectric constant material film) to be formed on theinsulating film 36.

Then, as shown in FIG. 16, the insulating film (low dielectric constantmaterial film) 37, an insulating film (silicon oxide film) 38, aninsulating film (low dielectric constant material film) 39 and aninsulating film (silicon oxide film) 40 are formed on the insulatingfilm 36 in the same manners as those of the insulating films 23, 24, 25,and 26. An opening (wiring groove) 41 is formed in the insulating films38, 39, and 40 and an opening (via) 42 is formed in the insulating films35, 36, and 37 in the same manners as those of the openings 29 and 31. Awiring (third layer wiring) 45, comprising a conductive barrier film 43and a main conductive film (copper film) 44 in which the openings 41 and42 are embedded, is formed in the same manner as that of the wiring 34.Thereafter, a barrier insulating film is formed, on the insulating film40 including the upper surface of the wiring 45, in the same manner asthose of the above-mentioned insulating films 21 and 22, and aninterlayer insulating film (low dielectric constant material film) andthe like are formed on the barrier insulating film, and further theupper layer wiring is formed. However, the explanation thereof will beomitted herein.

Examinations by the present inventors have found that, in thesemiconductor device having embedded copper wirings, the electricresistance of the embedded copper wiring is increased due to the stressmigration when it is left to stand at high temperature. At this time, anair gap or a void is formed between the upper surface of the lower layerembedded copper wiring and the via portion of the upper layer embeddedcopper wiring. For this reason, an area of the connection between thelower layer embedded copper wiring and the upper layer embedded copperwiring is reduced, whereby the increase in the electric resistanceoccurs. Further, there is the drawback of the occurrence of thedisconnection between the lower layer embedded copper wiring and theupper layer embedded copper wiring since the void is formed. Theseresult in reductions of the reliability of the wirings and themanufacturing yields of the semiconductor devices, and in an increase ofthe manufacturing costs.

Additionally, in the semiconductor device having the embedded copperwiring, it is also required to improve TDDB (Time Dependence onDielectric Breakdown) life of the embedded copper wiring. Note that theterm “TDDB life” means a scale for objectively measuring the timedependence of dielectric breakdown, wherein a relatively high voltage isimpressed between electrodes under the measurement condition of thespecified temperature (for example, 140° C.), and a graph in which thetime from the impression of voltage to the dielectric breakdown isplotted in regard to an impressed electric field is prepared, and thetime (life) obtained from this graph by extrapolating the strength ofthe actually used electric field (for example, 0.2 MV/cm) is called theTDDB time. According to the examinations by the present inventors, ithas been found that in the TDDB life tests, copper ions in the wiringare drifted by the electric field exerted between the adjacent wiringsin the embedded copper wirings disposed on the same layer, whereby thedielectric breakdown is caused.

Therefore, it is required to prevent the deterioration in the embeddedcopper wirings due to the stress migration and improve the TDDB life.

In the present embodiment, as barrier insulating films to cover theupper surface of the lower layer copper wiring (e.g., wiring 20), thefirst barrier insulating film (e.g., insulating film 21) and the secondbarrier insulating film (e.g., insulating film 22) are used, near thebottom of the via portion (e.g., conductive barrier film 32 and mainconductive film 33 embedded in the opening 31) of the upper layer copperwiring (e.g., wiring 34). As a first barrier insulating film disposed ona lower layer side (e.g., insulating film 21), a material film withexcellent barrier properties to copper (e.g., silicon carbonitride(SiCN) film) is used, and as a second barrier insulating film disposedon an upper layer side (e.g., insulating film 22), a material film(e.g., silicon carbide (SiC) film) with excellent adhesiveness to theinterlayer insulating film (low dielectric constant material film, e.g.,insulating film 23) is used. Thereby, it is possible to prevent thediffusion of copper in the copper wiring (e.g., wiring 20) and improvethe adhesiveness between the barrier insulating film (e.g., insulatingfilms 21 and 22) and the interlayer insulating film (low dielectricconstant material film, e.g., insulating film 23).

FIG. 17 is a graph showing the results of the TDDB life tests ofembedded copper wirings. The horizontal axis of the graph in FIG. 17corresponds to the strength of the electric field impressed between thewirings, and the vertical axis corresponds to the time from theimpression of the voltage to the dielectric breakdown. The time (life)obtained from this graph by extrapolating the strength of the actuallyused electric field (e.g., 0.2 MV/cm) can be considered as the TDDBlife.

In FIG. 17, in addition to the case of using a 25 nm thick siliconcarbonitride (SiCN) film as a first barrier insulating film (lowerlayer) and a 25 nm thick silicon carbide (SiC) film as a second barrierinsulating film (upper layer) as shown in the present embodiment (thiscase corresponding to white circles in the graph in FIG. 17), there arealso described the cases of using: a single layer of a 50 nm thicksilicon carbonitride (SiCN) film as a barrier insulating film, which isa first comparison example (this case corresponding to white squares inthe graph in FIG. 17 and to the case of omitting the formation of thesecond barrier insulating film in comparison to the present embodiment);a single layer of a 50 nm thick silicon carbide (SiC) film as a barrierinsulating film, which is a second comparison example (this casecorresponding to black squares in the graph in FIG. 17 and to the caseof omitting the formation of a first barrier insulating film incomparison to the present embodiment); and a 25 nm thick silicon carbide(SiC) film as a first barrier insulating film (lower layer) and a 25 nmthick silicon carbonitride (SiCN) film as a second barrier insulatingfilm (upper layer), which are a third comparison example (this casecorresponding to black circles in the graph in FIG. 17 and to the casewhere the first and second barrier insulating films are inverted incomparison to the present embodiment).

As seen from the graph in FIG. 17, in the present embodiment, since thebarrier insulating films are formed as a laminating structure and asilicon carbonitride (SiCN) film having excellent barrier properties tocopper is used in the first barrier insulating film contacting to theembedded copper wiring, it is possible to properly restrain or preventthe diffusion of copper in wirings and make the TDDB life of the wiringrelatively long (good). Meanwhile, if the silicon carbide (SiC) filmwhose barrier properties to copper is relatively inferior is used in thebarrier insulating film contacting to the embedded copper wiring (thiscase corresponding to the above-mentioned second and third comparisonexamples), then the copper in the wiring is easy to diffuse and the TDDBlife of the wiring deteriorates. As described in Non-patent Document 1,it is possible to improve the TDDB life of the wirings, by employing thesilicon carbonitride (SiCN) film having relatively excellent barrierproperties to copper rather than the silicon carbide (SiC) film using asthe barrier insulating film contacting to the embedded copper wiring.

FIGS. 18 to 20 each are a graph showing the resistance-rising ratioobtained after tests in which the embedded copper wirings are left tostand at the high temperature (e.g., being left at 150° C. for 100hours). Each horizontal axis in the graphs in FIG. 18 to FIG. 20corresponds to a change ratio or rise ratio (increase ratio of theelectric resistance obtained by regarding the electric resistance beforebeing left to stand at the high temperature test as a standard), andeach vertical axis in the graphs in FIG. 18 to FIG. 20 corresponds tothe cumulative distribution or the cumulative probability. FIG. 18corresponds to the case of using, as barrier insulating films of theembedded copper wirings, the laminated film of the first barrierinsulating film (lower layer) formed of a silicon carbonitride (SiCN)film (herein having a thickness of 25 nm) and the second barrierinsulating film (upper layer) formed of a silicon carbide (SiC) film(herein with a thickness of 25 nm) thereon. Further, FIG. 19 correspondsto the case of the above-mentioned first comparison example using, asthe barrier insulating film of the embedded copper wiring, a singlelayer of a 50 nm thick silicon carbonitride (SiCN) film. Also, FIG. 20corresponds to the case of the above-mentioned second comparison exampleusing, as the barrier insulating film of the embedded copper wiring, asingle layer of a 50 nm thick silicon carbide (SiC) film. Additionally,in each of FIGS. 18 to 20, experiments have been conducted for the casewhere the values of the wiring width are variously changed, and theresults thereof are plotted.

As seen from FIGS. 18 to 20, by being left to stand at the hightemperature, the electric resistance of the embedded copper wiring isincreased. In each of FIGS. 18 to 20, when the wiring width is setlarge, there is a trend toward the fact that the rise ratio of theelectric resistance of the embedded copper wiring often becomes large.

In the case of the above-mentioned first comparison example in which thesilicon carbonitride (SiCN) film having relatively low adhesiveness tothe low dielectric constant material film is used as a barrierinsulating film and the low dielectric constant material film is formedas an interlayer insulating film on the silicon carbonitride (SiCN)film, the rise ratio of the electric resistance of the embedded copperwiring by being left to stand at the high temperature becomes large, asshown in FIG. 19. It is thought that this is because when the lowdielectric constant material film as an interlayer insulating film isformed on the silicon carbonitride (SiCN) film as a barrier insulatingfilm, the adhesiveness (adhesion properties) between the barrierinsulating film and the low dielectric constant material film declinesnear the bottom of the via portion of the upper layer copper wiring,wherein failures due to the stress migration are easy to generate.

In contrast to this, as shown in FIG. 18 in the present embodiment, itis possible to restrain the rise of the electric resistance of theembedded copper wiring caused by being left to stand at the hightemperature, and to restrain or prevent occurrence of the failures dueto the stress migration.

In the present embodiment, since the barrier insulating films are formedas a laminating structure and the film having excellent adhesiveness tothe low dielectric constant material film (silicon carbide (SiC) film)is used as the second barrier insulating film contacting to the lowdielectric constant material film, it is possible to improve theadhesiveness between the barrier insulating films (e.g., insulatingfilms 21 and 22) and the interlayer insulating film (low dielectricconstant material film, e.g., insulating film 23). Therefore, it ispossible to improve the adhesiveness (adhesive strength) between thebarrier insulating films (e.g., insulating films 21 and 22) and theinterlayer insulating film (e.g., insulating film 23) near the bottom ofthe via portion (e.g., conductive barrier film 32 and main conductivefilm 33 embedded in the opening 31) of the upper layer copper wiring(e.g., wiring 34), and further to restrain or prevent the drawback dueto the above-mentioned stress migration, for example, the occurrence ofa gap or void between the via portion of the upper layer copper wiring(e.g., wiring 34) and the upper surface of the lower layer copper wiring(e.g., wiring 20), and the rise of the resistance between the upperlayer copper wiring (e.g., wiring 34) and the lower layer copper wiring(e.g., wiring 20), etc.

Note that the above-mentioned effects can be attained also in the caseswhere: the wiring 20 is applied as the lower layer copper wiring and thewiring 34 is applied as the upper layer copper wiring; the wiring 34 isapplied as the lower layer copper wiring and the wiring 45 is applied asthe upper layer copper wiring; and the wiring 45 is applied as the lowerlayer copper wiring and a further upper layer wiring (not illustrated)on the wiring 45 is applied as the upper layer copper wiring.

In the present embodiment, it is possible to improve not only thebarrier properties to copper between the copper wiring and the barrierinsulating film (prevention of the diffusion of copper) but also theadhesiveness between the barrier insulating film and the interlayerinsulating film (low dielectric constant material film), whereby theimprovements in the TDDB life and the stress migration characteristicsof the wirings can be achieved. Therefore, the reliability of thewirings can be improved. Additionally, it is possible to reduce themanufacturing yields of the semiconductor devices and further themanufacturing costs thereof.

Second Embodiment

FIGS. 21 and 22 each show a sectional view of the principal portion ofthe semiconductor device in the manufacturing process according toanother embodiment of the present invention. Since the manufacturingprocess from FIG. 1 to FIG. 5 in this case are the same as that of thefirst embodiment, the explanation thereof will be omitted here andmanufacturing process following FIG. 5 will be described hereinafter.Note that, also in FIGS. 21 and 22, the portions corresponding to thestructure illustrated below the insulation film 11 in FIG. 1 will beomitted.

After the structure shown in FIG. 5 is obtained, similarly to theabove-mentioned first embodiment, the reducing plasma treatment isperformed and then the cleaning is performed as occasion demands.Thereafter, as shown in FIG. 21, an insulating film (barrier insulatingfilm) 51 is formed by, for example, the plasma CVD method or the likeover the entirety of the main surface of the semiconductor substrate 1.Namely, the insulating film 51 is formed on the insulating film 16including the upper surfaces of the wirings 20.

The insulating film 51 is formed of a silicon carbonitride (SiCN) film,but a concentration distribution of nitrogen (N) in a thicknessdirection of the insulating film 51 is not uniform due to thebelow-mentioned reason.

Then, as shown in FIG. 22, on the insulating film 51, insulating films23, 24, 25, 26, and 27 are formed similarly to the above-mentioned firstembodiment.

FIG. 23 is a graph schematically showing a concentration distribution ofnitrogen (N) in a thickness direction (direction perpendicular to themain surface of the semiconductor substrate 1) of the insulating film51. The horizontal axis of the graph in FIG. 23 corresponds to positions(arbitrary unit), in the thickness (film thickness) direction from anupper area of the wiring 20 (or the insulating film 16) disposing underthe insulating film 51 to a lower area of the insulating film 23disposing on the insulating film 51, and the vertical axis of the graphin FIG. 23 corresponds to a concentration of nitrogen (N) (arbitraryunit) in the film.

As shown in the graph in FIG. 23, in the present embodiment, thenitrogen (N) concentration in the insulating film 51 disposed near aregion of the interface between the wiring 20 and the insulating film 51is larger than that of the insulating film 51 disposed near a region ofthe interface between the insulating film 51 and the upper insulatingfilm 23. For example, the insulating film 51 has a high nitrogen (N)concentration region 51 a at the lower portion (on a side of the wiring20 or insulating film 16) and a low nitrogen (N) concentration region atthe upper portion thereof (on a side of the insulating film 23).

The insulating film 51 may be formed continuously by, for example, theCVD method using a nitrogen gas. For example, in the initialfilm-forming stage of the insulating film 51, the insulating film 51 inthe high nitrogen concentration region 51 a can be formed by relativelyincreasing a flow amount of nitrogen gas introduced to a film-formingapparatus, and in the latter film-forming stage of the insulating film51, the insulating film 51 in the low nitrogen concentration region 51 bcan be formed by relatively decreasing the flow amount of nitrogen gasintroduced to the film-forming apparatus. Also, in the latterfilm-forming stage of the insulating film 51, the introduction of thenitrogen gas to the film-forming apparatus is stopped (zero flowamount), whereby the nitrogen concentration in the low nitrogenconcentration region 51 b of the insulating film 51 may be madeextremely small (or zero).

By increasing the nitrogen concentration in the silicon carbonitride(SiCN) film, it is possible to improve the barrier properties to copper(function of restraining or preventing the diffusion of copper) andenhance the breakdown property. Meanwhile, by decreasing the nitrogenconcentration in the silicon carbonitride (SiCN) film, it is possible toimprove the adhesiveness (adhesion properties) to the low dielectricconstant material film. When the low dielectric constant material filmis formed on the silicon carbonitride (SiCN) film whose nitrogenconcentration is high, there is the drawback of the fact that theadhesiveness (adhesion properties) between the underlying film (filmhaving a high nitrogen concentration) and the low dielectric constantmaterial film can be reduced. This causes the peeling between the films,whereby the reliability of the wirings is reduced. Such a phenomenon canbe generally caused in the above-mentioned low dielectric constantmaterials, and the occurrence thereof is especially prominent in thecase of using a material containing silicon (Si), oxygen (O), and carbon(C) as the low dielectric constant material, and is more prominent inthe case of using, for example, carbonated silicon (organic siliconglass, SiOC system material, for example, above-mentioned Black Diamondand the like), MSQ (methyl silsesquioxane) system material, or HSQ(hydrogen silsesquioxane) system material (including their porousmaterials) as the low dielectric constant material.

In the present embodiment, since the area that contacts to the wiring 20of the insulating film 51 made of silicon carbonitride (SiCN) is used asthe high nitrogen (N) concentration region 51 a, copper of the wiring 20can be adequately prevented from diffusing in the insulating film 51,and since the area that contacts to the insulating film (low dielectricconstant material film) 23 of the insulating film 51 is used as the lownitrogen (N) concentration region 51 b, the adhesiveness between theinsulating film 51 and the insulating film (low dielectric constantmaterial film) 23 can be improved. In this manner, since the nitrogen(N) concentration of the insulating film 51 in the area disposed nearthe interface between the wiring 50 and the insulating film 51 is madelarger than that of the insulating film 51 in the area disposed near theinterface between the insulating film 51 and the upper insulating film23, it is possible to improve both of the barrier properties to copperin the insulating film 51 and the adhesiveness to the upper lowdielectric constant material film. Further, the area that contacts tothe insulating film (low dielectric constant material film) 23 of theinsulating film 51 is constituted not by silicon carbide containing nonitrogen but by silicon carbonitride (SiCN). Therefore, it is possibleto further enhance the function of the copper-diffusing prevention andthe breakdown property in the entirety of the barrier insulating film51.

FIGS. 24 and 25 each show a sectional view showing the principal portionof the semiconductor device in the manufacturing process following FIG.22. Note that, also in both FIGS. 24 and 25, the portions correspondingto the structure illustrated below the insulating film 11 in FIG. 1 willbe omitted.

After the structure shown in FIG. 22 is obtained, the same process asthat corresponding to FIGS. 8 to 13 in the first embodiment areperformed, and the openings 29 and 31 and the wiring 34 embedded thereinare formed, and thereafter the structure shown in FIG. 24 is obtained.Then, as shown in FIG. 25, an insulating film 52, made of the samematerial as and having the same concentration distribution of nitrogen(N) as that of the insulating film 51, is formed as a barrier insulatingfilm on the insulating film 26 including the upper surfaces of thewirings 34. Then, similarly to the first embodiment, on the insulatingfilm 52 used as a barrier insulating film, insulating films 37, 38, 39,and 40 are formed and the openings 41 and 42 are formed and further awiring 45 comprising a conductive barrier film 43 and a copper mainconductive film 44, which are embedded in the openings 41 and 42, isformed. Thereafter, in the same manner as that for forming theinsulating film 51, a barrier insulating film is formed on theinsulating film 40 including the upper surface of the wiring 45, and aninterlayer insulating film (low dielectric constant material film) andthe like are formed on the barrier insulating film, and further an upperlayer wiring is formed thereon. However, the explanation thereof will beomitted herein.

In the present embodiment, at the area near the bottom of the viaportion (the conductive barrier film 32 and the main conductive 33embedded in the opening 31) of the upper layer copper wiring (wiring34), the insulating film 51 is used as a barrier insulating film forcovering the upper surface of the lower layer copper wiring (the wiring20). The insulating film 51 is formed of a silicon carbonitride (SiCN)film, but the concentration distribution of nitrogen (N) in thethickness direction of the insulating film 51 is not uniform. In thepresent embodiment, the nitrogen (N) concentration of the insulatingfilm 51 at the area disposed near the interface between the wiring 20and the insulating film 51 is larger than that of the insulating film 51at the area disposed near the interface between the insulating film 51and the upper insulating film 23. Therefore, it is possible to achieveboth improvements of the barrier properties (diffusion prevention) tocopper between the copper wiring (wiring 20) and the barrier insulatingfilm (insulating film 51) and of the adhesiveness between the barrierinsulating film (insulating film 51) and the interlayer insulating film(low dielectric constant material film, insulating film 23). Sucheffects can be obtained respectively from the insulating film 51 used asthe barrier insulating film of the wiring 20, the insulating film 52used as the barrier insulating film of the wiring 34, and the barrierinsulating film (not illustrated) of the wiring 45. For this reason, itis possible to realize improvements of the TDDB life and the stressmigration characteristics of the wirings. Therefore, the reliability ofthe wirings can be improved. Additionally, it is possible to improve themanufacturing yields and reduce the manufacturing costs of thesemiconductor devices.

Further, the first embodiment and the present embodiment can be used incombination. Namely, the wiring (wiring layer) using the barrierinsulating film comprising a laminated film of the insulating films 21and 22 (or the insulating films 35 and 36) as described in the firstembodiment, and the wiring (wiring layer) using the barrier insulatingfilm comprising the insulating film 51 (or insulating film 52) asdescribed in the present embodiment can be also used in combination.

Third Embodiment

FIGS. 26 to 32 show sectional views showing the principal portion of thesemiconductor device in the manufacturing process according to anotherembodiment of the present invention. Since the manufacturing process inshown in FIGS. 1 to 9 in this case is the same as that of the firstembodiment, the explanations thereof will be omitted here and themanufacturing process following FIG. 9 will be explained hereinafter.Note that, also in FIGS. 26 to 32, the portions corresponding to thestructure illustrated below the insulation film 11 in FIG. 1 will beomitted.

After the structure shown in FIG. 9 is obtained, as shown in FIG. 26, aninsulating film 61 as a second hard mask layer is formed on theinsulating film 27 so as to fill the opening 29 therewith. Theinsulating film 61 may be made of such a material as, for example, asilicon oxide (SiO) film, silicon oxynitride (SiON) film, siliconoxycarbide (SiOC) film or the like, whose an etching selection ratio isdifferent from those of the insulating films 24 and 27 and also from theinsulating film 25.

Next, as shown in FIG. 27, a photoresist film is formed on theinsulating film 61 and the photoresist film is exposed, developed andpatterned, whereby a photoresist pattern 62 is formed. Then, by usingthe photoresist pattern 62 as an etching mask, the insulating film 61 isdry etched to form an opening 31 in the insulating film 61. Note thatthe opening 31 is formed in the area for forming a via and a plane areaof the opening (via) 31 is included in that of the opening (wiringgroove) 29. Thereafter, the photoresist pattern 62 is removed by theashing or the like.

Then, as shown in FIG. 28, by using the insulating film 61 as an etchingmask (hard mask), the insulating films 26 and 25 are dry etched at thebottom of the opening 31. Thereafter, the insulating film 61 is removedby the dry etching or the like.

Next, as shown in FIG. 29, by using the insulating film 27 as an etchingmask (hard mask), the insulating films 26 and 25 are dry etched at thebottom of the opening 29, and the insulating films 24 and 23 are dryetched at the bottom of the opening 31. At the time of this dry etching,the insulating film 22 (and the insulating film 21) functions as anetching stopper film. Since the insulating films 21 and 22 exist(remain) at the bottom of the opening 31, it is possible to prevent thewirings 20 from being etched.

Next, as shown in FIG. 30, the insulating film 24 is removed by the dryetching at the bottom of the opening 29, and the insulating films 22 and21 are removed by the dry etching at the bottom of the opening 31. Inthis manner, the upper surface of the wiring 20 is exposed from thebottom of the opening 31. Further, the insulating film 27 is removed bythe dry etching. The insulating film 27 may be removed by the same dryetching as that in the step of removing the insulating films 22 and 21at the bottom of the opening 31, or by another dry etching differenttherefrom. The insulating film 26 left after removing the insulatingfilm 27 can function as a protective film and the like in the CMPtreatment.

Next, as shown in FIG. 31, in the same manners as those in the firstembodiment, the conductive barrier film 32 and the wiring 34 comprisingthe main conductive film 33 of copper are formed in the openings 29 and31. Then, as shown in FIG. 32, on the insulating film 26 including theupper surfaces of the wirings 34 in the same manners as those in thefirst embodiment, insulating films 35, 36, 37, 38, 39, and 40 areformed; by using the same step as that of forming the openings 29 and 31in the present embodiment, openings 41 and 42 are formed in theinsulating films 35 to 40; and, in the same manners as those in thefirst embodiment, a wiring 45 comprising a conductive barrier film 43and a main conductive film 44 of copper are formed in the openings 41and 42. Thereafter, on the insulating film 40 including the uppersurface of the wiring 45, a barrier insulating film is formed in thesame manners as those of the above-mentioned insulating films 21 and 22,and further an interlayer insulating film (low dielectric constantmaterial film) and the like are formed on the barrier insulating film,and further an upper layer wiring is formed thereon. However, theexplanations thereof will be omitted herein.

In the present embodiment, the same effects as those in the firstembodiment can be attained. Further, in the present embodiment, when theinsulating films 23 and 25 formed of low dielectric constant materialsare dry etched for forming the openings 29 and 31, the insulating films61 and 27 are used as hard masks without using the photoresist patternas an etching mask. For this reason, in such a state that the insulatingfilms 23 and 25 formed of the low dielectric constant materials areexposed, the photoresist pattern is not removed (ashed). Accordingly, itis possible to prevent the low dielectric constant material films (theinsulating films 23 and 25) from being changed in quality (damaged) atthe time of ashing the photoresist pattern or the like. Thereby, it ispossible to further improve the reliability of the semiconductordevices.

Furthermore, the second embodiment and the present embodiment may beused in combination.

Fourth Embodiment

FIGS. 33 to 42 show sectional views showing the principal portion of thesemiconductor device in the manufacturing process according to anotherembodiment of the present invention. Since the manufacturing process ofFIGS. 1 to 6 are the same as that in the first embodiment, theexplanations thereof will be omitted and the manufacturing processfollowing FIG. 6 will be explained hereinafter. Note that, also in FIGS.33 to 42, the portions corresponding to the structure illustrated belowthe insulation film 11 in FIG. 1 will be omitted.

In the first to third embodiments, the wiring 34 (wiring 45) is formedusing a so-called Dual-Damascene technique. In the present embodiment,the wiring 34 (wiring 45) is formed using a so-called Single-Damascenetechnique.

After the structure shown in FIG. 6 is obtained, as shown in FIG. 33, inthe same manners as those in the first embodiment, the insulating films23 and 24 are formed on the insulating film 22. Then, in the presentembodiment, an insulating film (hard mask layer) 71 comprising, forexample, a silicon nitride film (SiN), silicon carbide (SiC) film,silicon carbonitride (SiCN) film, aluminum oxide (AlO) film, or the likeis formed on the insulating film 24. Then, a photoresist pattern 72 isformed on the insulating film 71 by using a photolithography method.

Next, as shown in FIG. 34, by using the photoresist pattern 72 as anetching mask, the insulating film 71 is dry etched, and thereby anopening 31 a is formed in the insulating film 71. Note that the opening31 a is formed in the area for forming a via, and corresponds to theopening 31 in the first embodiment. Thereafter, the photoresist pattern72 is removed by the ashing or the like.

Next, as shown in FIG. 35, by using the insulating film 71 as an etchingmask (hard mask), the insulating films 24 and 23 are dry etched. Since aphotoresist pattern is not used in dry etching the insulating film 23made of a low dielectric constant material, it is possible to preventthe insulating film (low dielectric constant material film) 23 frombeing deteriorated in quality (damaged) due to the removing (ashing) ofthe photoresist pattern. Further, at the time of this dry etching, sincethe insulating film 22 (and the insulating film 21) is made to functionas an etching stopper film, the insulating films 22 and 21 are left atthe bottom of the opening 31 a, whereby it is possible to prevent thewiring 20 from being etched.

Next, as shown in FIG. 36, at the bottom of the opening 31 a, theinsulating films 22 and 21 are removed by the dry etching. Thereby, theupper surface of the wiring 20 is exposed from the bottom of the opening31 a. And, the insulating film 71 is removed by the dry etching. Theinsulating film 71 may be removed by the same dry etching as that in thestep of removing the insulating films 22 and 21 at the bottom of theopening 31 a, or by another dry etching different therefrom. Theinsulating film 24 left after removing the insulating film 71 canfunction as a protective film in the CMP treatment and the like in thesame manners as those of the insulating films 16 and 26 in the firstembodiment, and can be formed by, for example, a silicon oxide (SiO)film.

Next, as shown in FIG. 37, similarly to the step of forming the wiring20, a plug 75 comprising a conductive barrier film 73 and a copper mainconductive film 74 are formed in the opening 31 a. For example, on theentirety of the main surface of the semiconductor substrate 1 (on theinsulating film 24 including the bottom and side walls of the opening 31a), a conductive barrier film 73 made of, for example, titanium nitride(TiN) and the like is formed; a main conductive film 74 made of copper(or copper alloy) is formed on the conductive barrier film 73 so as tofill (bury) the inside of the opening 31 a therewith; and the mainconductive film 74 and the conductive barrier film 73 are polished by,for example, the CMP method until the upper surface of the insulatingfilm 24 is exposed. In this manner, the unnecessary conductive barrierfilm 73 and main conductive film 74 on the insulating film 24 areremoved, and then the conductive barrier film 73 and the main conductivefilm 74 are left respectively in the opening 31 a, whereby the plug 75comprising the relatively thin conductive barrier film 73 and therelatively thick main conductive film 74 is formed. The formed plug 75is electrically connected to the wiring 20.

Then, after the reducing plasma and/or the cleaning as occasion demandsare performed, as shown in FIG. 38, on the entirety of the main surfaceof the semiconductor substrate 1 (on the insulating film 24 includingthe upper surface of the plug 75), an insulating film 76 including, forexample, a silicon nitride film and the like is formed, and theinsulating films 25, 26, and 27 are formed on the insulating film 76similarly to the first embodiment. If unnecessary, the formation of theinsulating film 76 may be omitted. And, a photoresist pattern 77 isformed on the insulating film 27 by the photolithography method.

Next, as shown in FIG. 39, by using the photoresist pattern 77 as anetching mask, the insulating film 27 is dry etched to form openings 29 ain the insulating film 27. Note that the opening 29 a is formed in thearea for forming a wiring groove, and corresponds to the opening 29 inthe first embodiment. Therefore, the plane area of the opening 29 aincludes that of the opening 31 a. Then, the photoresist pattern 77 isremoved by the ashing or the like.

Next, as shown in FIG. 40, by using the insulating film 27 as an etchingmask (hard mask), the insulating films 26 and 25 are dry etched. Whenthe insulating film 25 formed of the low dielectric constant materialfilm is dry etched, no photoresist patter is used, whereby it ispossible to prevent a deterioration in quality (damage) of theinsulating film 25 (the low dielectric constant material film) causeddue to the removing (ashing) of the photoresist pattern. Then, at thebottoms of the openings 29 a, the insulating film 76 is removed by thedry etching. For this reason, from the bottoms of the openings 29 a, theupper surfaces of the wirings 20 are exposed. Note that, if theformation of the insulating film 76 is omitted, the upper surfaces ofthe wirings 20 are exposed from the bottoms of the openings 29 a by thedry etching of the above-mentioned insulating films 26 and 25. And, theinsulating film 27 is removed by the dry etching. The insulating film 27may be removed by the same dry etching as that in the step of removingthe insulating film 76 at the bottom of the opening 29 a, or by anotherdry etching different therefrom. The insulating film 26 left after theinsulating film 27 is removed can function as a protective film in theCMP treatment or the like.

Next, as shown in FIG. 41, similarly to the step of forming the wiring20, a wiring (second layer wiring) 80 formed of a conductive barrierfilm 78 and a copper main conductive film 79 is formed in the opening 29a. For example, on the entirety of the main surface of the semiconductorsubstrate 1 (on the insulating film 26 including the bottom and sidewalls of the opening 29 a), a conductive barrier film 78 made of, forexample, titanium nitride (TiN) and the like is formed; a mainconductive film 79 made of copper (or copper alloy) is formed on theconductive barrier film 78 so as to fill (bury) the inside of theopening 29 a therewith; and the main conductive film 79 and theconductive barrier film 78 are polished by, for example, the CMP methoduntil the upper surface of the insulating film 26 is exposed. In thismanner, the unnecessary conductive barrier film 78 and main conductivefilm 79 on the insulating film 26 are removed and the conductive barrierfilm 78 and the main conductive film 79 are left in the opening 29 a,whereby a wiring 80 comprising a relatively thin conductive barrier film78 and a relatively thick main conductive film 79 is formed in theopening 29 a. The formed wiring 80 is electrically connected to thewiring 20 via the plug 75.

Then, as shown in FIG. 42, the insulating films 35 and 36 as barrierinsulating films are formed on the wirings 80, similarly to the firstembodiment. Then, similarly to the step of forming the plug 75 and thewiring 80 in the present embodiment, further upper layer plug and wiringelectrically connected to the wiring 80 are formed. However, theexplanations thereof will be omitted here.

In the present embodiment, the same effects as those in the firstembodiment can be attained. Further, in the present embodiment, when theinsulating films 23 and 25 made of the low dielectric constant materialsare dry etched for forming the openings 31 a and 29 a, the insulatingfilms 71 and 27 are used as hard masks without using the photoresistpattern as an etching mask. Therefore, in such a state that theinsulating films 23 and 25 made of the low dielectric constant materialsare exposed, the photoresist pattern is not removed (ashed).Accordingly, it is possible to prevent the low dielectric constantmaterial films (the insulating films 23 and 25) from being deterioratedin quality (or damaged) due to the ashing of the photoresist pattern orthe like. This can further improve the reliability of the semiconductordevices.

Moreover, the second embodiment and the present embodiment may be usedin combination.

Fifth Embodiment

FIGS. 43 to 46 show sectional views showing the principal portion of thesemiconductor device in the manufacturing process according to anotherembodiment of the present invention. Since the manufacturing process ofFIGS. 1 to 5 in this case is the same as that in the first embodiment,the explanations thereof will be omitted here and the manufacturingprocess following FIG. 5 will be explained hereinafter. Note that, alsoin FIGS. 43 to 46, the portions corresponding to the structureillustrated below the insulation film 11 in FIG. 1 will be omitted.

After the structure shown in FIG. 5 is obtained, as shown in FIG. 43, afilm 91 (i.e., approximately 20 nm or less) is formed near the surfaceof the main conductive film 19 of the wiring 20. The film 91 is made ofa copper (Cu) compound whose a diffusion coefficient is smaller thanthat of copper (Cu), or made of metal other than copper (Cu).

The film 91 may, for example, be formed as follows. After the structureshown in FIG. 5 is obtained, the ammonia (NH₃) plasma treatment or thelike is performed to the semiconductor substrate 1 in such a state thatthe surface of the wiring 20 is exposed, and a copper nitride (CuN) filmis formed on the surface of the wiring 20, and thereby the film 91 madeof copper nitride (CuN) may be formed. At this time, it is furtherpreferred that the cleaning treatment is performed on the surfaces ofthe wirings 20 (and the surface of the insulating film 16) and thesurfaces of the wirings 20 are cleaned, and thereafter the film 91 madeof copper nitride (CuN) is formed on the cleaned surfaces of the wirings20.

Or, the film 91 may be formed as follows. The ammonia (NH₃) plasmatreatment is performed to the semiconductor substrate 1 in such a statethat the surface of the wiring 20 is exposed, and thereafter a monosilane gas or the like is sprayed thereon, and thereby a copper layer(CuSi_(x) layer) containing (added by) a small quantity (e.g.,approximately 1 to 2 atom %) of silicon (Si) is formed on the surface ofthe wiring 20 and the film 91 made of copper to which silicon is addedmay be formed. Further, also by using a copper layer (CuAl_(x) layer) towhich a small quantity of aluminum (Al) is added, the film 91 may beformed.

Or, the film 91 may be formed also by using a selective tungsten CVDmethod or the like. For example, after the structure shown in FIG. 5 isobtained, a tungsten film is selectively deposited on the surface of thewiring 20 exposed from the insulating film 16, by the CVD method usingtungsten hexafluoride (WF₆) and a hydrogen (H₂) gas, and thereby thefilm 91 made of tungsten may be formed.

Or, the film 91 may be formed also by using a selective plating methodor the like. For example, after the structure shown in FIG. 5 isobtained, a plating layer such as a Co film or a WB film is selectivelyformed on the surface of the wiring 20 exposed from the insulating film16, and thereby the film 91 formed of a plating layer (e.g., Co or WBfilm) may be formed.

After the film 91 is formed, the structure shown in FIG. 44 is obtainedby performing the same process as that corresponding to FIGS. 6 to 13 inthe first embodiment. Then, as shown in FIG. 45, near the surface (e.g.,approximately 20 nm or less) of the main conductive film 33 of thewiring 34, a film 92 made of the same material as that of the film 91 isformed in the same manner. After the film 92 is formed, the structure ofFIG. 46 can be formed by performing the same process as thatcorresponding to FIGS. 15 and 16 in the first embodiment, and thestructure of FIG. 46 may be formed. However, in the present embodiment,also as for the wiring 45, a film 93 made of the same material as thatof the film 91 is formed by the same manners near the surface of themain conductive film 44 of the wiring 45.

In the present embodiment, the film 91 is formed on the surface of thewiring 20, and the insulating film 21 as a barrier insulating film isformed on the film 91. Unless the film 91 is present, a film is made bya copper compound (or metal other than copper) whose diffusioncoefficient is smaller than that of copper (Cu) and which arises from abounding state of the interface between the copper film (main conductivefilm 19) and the barrier insulating film (insulating film 21), and thensuch a film is interposed between the copper film (main conductive film19) and the barrier insulating film (insulating film 21). The wirings 34and 45 are also formed in the same manner as described above. Therefore,it is possible to restrain the diffusion of copper in the interfacebetween the wiring and the barrier insulating film, and further improvethe stress migration characteristics of the wirings and the like.

Further, the first to fourth embodiments and the present embodiment maybe used in combination.

Sixth Embodiment

FIG. 47 shows a sectional view showing the principal portion of thesemiconductor device in the manufacturing process according to anotherembodiment of the present invention. FIG. 47 corresponds to FIG. 16 inthe first embodiment. Note that, also in FIG. 47, the portionscorresponding to the structure illustrated below the insulation film 11in FIG. 1 will be omitted.

The semiconductor device shown in FIG. 47 has the same structure as thatin FIG. 16. In the present embodiment, a barrier insulating film of anembedded copper wiring (e.g., wiring 20) is constituted by a laminatedfilm of a first barrier insulating film (e.g., insulating film 21) and asecond barrier insulating film (e.g., insulating film 22), wherein thestress S1 of the laminated film is set at −180 MPa or more (S₁≧−180MPa). Note that, in the present embodiment, if the stress (stress value)of a certain film is referred to, it means the stress (film stress)caused when such a film is formed directly on the semiconductorsubstrate 1 formed of a silicon substrate. Therefore, in the case wherethe stress of the laminated film of the first and second barrierinsulating films is −180 Mpa or more, such stress corresponds to onecaused in the laminated film at the time when the first and secondbarrier insulating films are formed directly on the semiconductorsubstrate 1. Further, when the stress S₁ of the laminated film is −180MPa or more, such stress corresponds to one obtained by a combination of−180 MPa≦S₁≦0 and 0≦S₁.

FIG. 48 is a graph showing the stress (stress value) S1 of a laminatedfilm of the insulating films 21 and 22 at the time when the insulatingfilm 21 is formed of a silicon carbonitride (SiCN) film and theinsulating film 22 is formed of a silicon carbide (SiC) film and theentire thickness of the laminated film of the insulating films 21 and 22is made (fixed) 50 nm and the ratio of each thickness of the insulatingfilms 21 and 22 is changed. The horizontal axis of the graph in FIG. 48corresponds to the thickness of the silicon carbonitride film(insulating film 21) at the time when the entire thickness of thelaminated film of the silicon carbonitride film (insulating film 21) andthe silicon carbide film (insulating film 22) is made (fixed) 50 nm. Thevertical axis of the graph in FIG. 48 corresponds to the stress (stressvalue) S1 of the laminated film.

As seen from FIG. 48, the stress of the single film of the siliconcarbonitride (SiCN) film (corresponding to the case where the thicknessof the silicon carbonitride (SiCN) film in the horizontal axis in FIG.48 is 50 nm) has a negative value, and so compression stress occurs.Meanwhile, the stress of the single film of the silicon carbide (SiC)film (corresponding to the case where the thickness of the siliconcarbonitride (SiCN) film in the horizontal axis in FIG. 48 is 0 nm) hasa positive value, and therefore tensile stress occurs. In the singlefilm of the silicon carbonitride (SiCN) film, relatively large negativestress occurs. However, as shown in FIG. 48, by decreasing the thicknessof the silicon carbonitride (SiCN) film and increasing the ratio of thethickness of the silicon carbide (SiC) film, the stress of the entiretyof the laminated film shifts to the positive-value direction.

According to the experiments by the present inventors, it has been foundthat when the thickness of the insulating film 21 becomes 40 nm or lessand the stress of the laminated film of the insulating films 21 and 22becomes −180 MPa or more, the preferable stress migrationcharacteristics can be obtained. For example, if the laminated filmwhose stress becomes −180 MPa or more is used as the barrier insulatingfilm disposed between the lower layer copper wiring and the interlayerinsulating film (low dielectric constant material film), the results ofthe tests of being left to stand at 150° C. for 100 hours have indicatedthat the change ratio (rise ratio) of the electric resistance in theembedded copper wiring could be restrained within 2%. Meanwhile, if thelaminated film whose stress is smaller than −180 MPa (S₁<−180 MPa) isused as a laminated film disposed between the lower layer copper wiringand the interlayer insulating film (low dielectric constant materialfilm), the results of the test of being left to stand at 150° C. for 100hours have indicated that the change ratio (rise ratio) of the electricresistance of the embedded copper wiring exceeds 2% in some cases. Ifthe laminated film is used as a barrier insulating film disposed betweenthe lower layer copper wiring and the interlayer insulating film (lowdielectric constant material film) and if the stress of the laminatedfilm is −180 MPa or more, relaxation of the stress caused by being leftto stand at the high temperature is difficult to make and it is possibleto prevent the occurrence of problems arising from the stress migration.

In the present embodiment, the insulating film 21 whose barrierproperties to copper are superior (to the insulating film 22) can bemade to function as a barrier insulating film (copper diffusionprevention film) of the wiring 20, and the insulating film 22 can bemade to function as a film for controlling the stress. For example, theinsulating film 22 can function to relax the stress generated in theinsulating film 22. In the single film of the insulating film 21 withexcellent barrier properties to copper, even if the stress is not in adesirable range (wherein the stress is −180 MPa or more), then theinsulating film 22 is formed on the insulating film 21 to control thestress of the entirety of the laminated film, for example, the negativestress (compression stress) that the insulating film 21 generates isrelaxed by the positive stress (tensile stress) that the insulating film22 generates, whereby the entire stress of the laminated film (barrierinsulating films) can be controlled to be −180 MPa or more and theadhesiveness (adhesion properties) between the laminated film (barrierinsulating film) and the interlayer insulating film (low dielectricconstant material film) can be improved. Consequently, it is possible torestrain the problems arising from the stress migration (e.g.,occurrence of the void between the upper surface of the lower layerembedded copper wiring and the via portion of the upper layer embeddedcopper wiring, which is caused by being left to stand at the hightemperature, and the rising of the electric resistance of the embeddedcopper wiring, etc.) and to improve the reliability of the wirings.Therefore, the reliability of the semiconductor devices can be improved.Additionally, it is possible to reduce the manufacturing yields and themanufacturing costs of the semiconductor devices.

Further, the first to fifth embodiments and the present embodiment maybe used in combination.

Seventh Embodiment

FIGS. 49 to 51 show sectional views showing the principal portion of thesemiconductor device in the case where another manufacturing processother than that in the first embodiment is used. Since the manufacturingprocess of FIGS. 1 to 6 is the same as that in the first embodiment, theexplanations thereof will be omitted here and the manufacturing processfollowing FIG. 6 will be explained hereinafter. Note that, also in FIGS.49 to 51, the portions corresponding to the structure illustrated belowthe insulation film 11 in FIG. 1 will be omitted.

As shown in FIG. 49, the insulating film (interlayer insulating film)23, the insulating film (etching stopper film) 24, the insulating film(interlayer insulating film) 25, and the insulating film (CMP protectionfilm) 26 are formed on the insulating film 22 in this order,respectively. These insulating films 23 to 26 can be formed by using thesame materials as those used in the first embodiment.

Next, a photoresist film is formed on the insulating film 26, and thephotoresist film is exposed, developed, and patterned, and thereby aphotoresist pattern 101 is formed. Then, by using the photoresistpattern 101 as an etching mask, the insulating films 26 and 25 are dryetched. Thereby, the opening 31 is formed in the insulating films 25 and26. The opening 31 is formed in the area for forming a via. Therefore,the plane area of the opening 31 is included in that of the opening 29as described hereinafter. Further, at the time of the dry etching, theinsulating film 24 functions as an etching stopper film.

Next, after the photoresist pattern 101 is removed, as shown in FIG. 50,a photoresist film is formed on the insulating film 26 and thephotoresist film is exposed, developed, and patterned, and thereby aphotoresist pattern 102 is formed. Then, by using the photoresistpattern 102 as an etching mask, first, the insulating films 24 and 26are dry etched. Thereafter, by dry etching the insulating film 25 andthe insulating film 26 in the opening 31, the openings 31 and 29 can beformed in the insulating films 23 and 25, respectively. At the time ofthis dry etching, the insulating film 24 functions as an etching stopperfilm in the opening 29, and the insulating films 22 and 21 function asetching stopper films in the opening 31.

Next, as shown in FIG. 51, the insulating film 24 is removed by the dryetching at the bottom of the opening 29, and the insulating films 22 and21 are removed by the dry etching at the bottom of the opening 31.Thereafter, the photoresist pattern 102 is removed. Thereby, the uppersurface of the wiring 20 is exposed from the bottom of the opening 31.Note that the residual insulating film 26 can function as a protectionfilm or the like in the CMP treatment to be performed later.

Next, the copper oxide, formed on the surface of the wiring 20 (lowerlayer copper wiring) exposed from the bottom of the opening 31, isremoved, and a cleaning treatment of the exposed surface of the wiring20 is performed. This cleaning treatment can be performed by thereducing plasma treatment such as a hydrogen (H₂) plasma treatment inwhich copper oxide (CuO, Cu₂O, CuO₂) on the surface of the copper wiringis reduced into copper (Cu).

The manufacturing process hereafter is made in the same manner as thatfollowing FIG. 13 in the first embodiment. Therefore, the wiring 34 canbe formed by filling the openings 29 and 31, with the conductive barrierfilm 32 made of the same material as that of the conductive barrier film18 and the main conductive film 33 made of the same material as that ofthe main conductive film 19.

As mentioned above, even when the manufacturing process as shown in thepresent embodiment is used for formation, it is possible to achieve,similarly to the first embodiment, both improvements of the barrierproperties to copper between the copper wiring and the barrierinsulating film (copper diffusion prevention) and of the adhesivenessbetween the barrier insulating film and the interlayer insulating film(low dielectric constant material film). Accordingly, the improvementsof the TDDB life of the wirings and of the stress migrationcharacteristics can be achieved. Thereby, the reliability of the wiringscan be improved. Additionally, it is possible to reduce themanufacturing yields and the manufacturing costs of the semiconductordevices.

Further, the second, fifth, or sixth embodiment and the presentembodiment may be used in combination.

Eighth Embodiment

FIGS. 52 to 55 show sectional views showing the principal portion of thesemiconductor device in another manufacturing process in which a mask(photoresist pattern) is used in the seventh embodiment. Similarly tothe seventh embodiment, since the manufacturing process of FIGS. 1 to 6is the same as that in the first embodiment, the explanations thereofwill be omitted here and the manufacturing process following FIG. 6 willbe explained hereinafter. Note that, also in FIGS. 52 to 55, theportions corresponding to the structure illustrated below the insulationfilm 11 in FIG. 1 will be omitted.

As shown in FIG. 52, on the insulating film 22, an insulating film(interlayer insulating film) 23 and an insulating film (CMP protectivefilm) 26 are formed in this order. These insulating films 23 and 26 maybe formed using the same materials as those used in the firstembodiment. Further, the thickness of the insulating film 23 in thepresent embodiment is relatively thicker than that of the insulatingfilm 23 in the first embodiment and, for example, substantiallycorresponds to the total thickness of the insulating films 23 and 25 (orthe insulating films 23 to 25) in the first embodiment. In the presentembodiment, the formation of the insulating film 24 is omitted. This isfor achieving a reduction in the capacity between wirings, the capacityreduction being described later. Namely, the insulating film 23 is a lowdielectric constant material film as shown in the first embodiment whilethe insulating film 24 is formed of a silicon oxide film and the like.For this reason, the insulating film 24 would have a higher dielectricconstant than that of the insulating film 23. Accordingly, by omittingthe forming of such a insulating film 24, the reduction in the capacitybetween the wirings can be achieved.

Next, a photoresist film is formed on the insulating film 26, and thephotoresist film is exposed, developed and patterned, and thereby aphotoresist pattern 101 is formed. Then, by using the photoresistpattern 101 as an etching mask, the insulating films 26 and 23 are dryetched. Thereby, the opening 31 going through (reaching to) theinsulating film 22 is formed in the insulating films 26 and 23. At thistime, by using an etching gas whose selectivity ratio is different fromthose of the insulating films 22 and 23, the insulating film 22functions as an etching stopper, whereby the over etching to the wiring20 can be prevented.

Next, after the photoresist pattern 101 is removed, as shown in FIG. 53,a photoresist film is formed on the insulating film 26, and thephotoresist film is exposed, developed, and patterned, and thereby aphotoresist pattern 102 is formed. Then, by using the photoresistpattern 102 as an etching mask, the insulating films 26 and 23 are dryetched. By controlling the etching time so as to become shorter than thetime for forming the above-mentioned opening 31, the opening 29 may beformed. Also at this time, the insulating film 22 functions as anetching stopper.

Next, as shown in FIG. 54, the insulating films 22 and 21 are removed atthe bottom of the opening 31 by the etching. Thereafter, the photoresistpattern 102 is removed. Thereby, from the bottom of the opening 31, theupper portion of the wiring 20 is exposed. Note that the insulating film26 left thereon can function as a protective film in the CMP treatmentand the like.

Next, the copper oxide, formed on the surface of the wiring 20 (lowerlayer copper wiring) exposed from the bottom of the opening 31, isremoved and a cleaning treatment of the exposed surface of the wiring 20is performed. This cleaning treatment may be performed by the reducingplasma treatment such as a hydrogen (H₂) plasma treatment in whichcopper oxide (CuO, Cu₂O, CuO₂) on the surface of the copper wiring isreduced into copper (Cu).

The manufacturing process hereafter is the same as that subsequent toFIG. 13 in the first embodiment, and in the openings 29 and 31. Thewiring 34 as shown in FIG. 55 may be formed by filling the openings 29and 31, with the conductive barrier film 32 made of the same material asthat of the conductive barrier film 18 and the main conductive film 33made of the same material as that of the main conductive film 19.

Thus, in the present embodiment, the insulating film 24 whose dielectricconstant is higher than that of the insulating film 23 is not formed andthe formation of the opening 29 is made by controlling the time of theetching gas, whereby the capacity between the wirings can be reduced.Additionally, since the formation of the insulating film 24 can beomitted, a simplification of the manufacturing process can be achieved.

Moreover, even when the manufacturing process shown in the presentembodiment is used for formation, it is possible to achieve, similarlyto the first embodiment, both improvements of the barrier properties tocopper between the copper wiring and the barrier insulating film (copperdiffusion prevention) and of the adhesiveness between the barrierinsulating film and the interlayer insulating film (low dielectricconstant material film). For this reason, it is possible to improve theTDDB life of the wirings and the stress migration characteristics.Thereby, the reliability of the wirings can be improved. Additionally,the manufacturing yields and further the manufacturing costs of thesemiconductor devices can be reduced.

And, at the time of forming the openings 29 and 31 in the presentembodiment, the insulating films 27 and 61 may be used as masks asdescribed in the third embodiment. In this case, the photoresist patternis not removed (ashed) in such a state that the insulating film 23 madeof the low dielectric constant material is exposed. Accordingly, it ispossible to prevent change in quality of (damage to) the low dielectricconstant material film (insulating film 23), which is caused by ashingor the like the photoresist pattern.

Further, the second, fifth, or sixth embodiment and the presentembodiment may be used in combination.

In the foregoing, the inventions made by the inventors have beenspecifically described based on the embodiments thereof. However,needless to say, the present invention is not limited to theabove-mentioned embodiments and can be variously modified and alteredwithout departing from the gist thereof.

In the above-mentioned embodiments, the semiconductor device having anMISFET has been explained. However, the present invention is not limitedto this, and may be applied to various semiconductor devices, each ofwhich has wirings including main conductive films each containing copperas a primary component.

The effects obtained by representative ones among the inventionsdisclosed in this application will be briefly described as follows.

It is possible to improve the reliability of the copper wirings by usingthe laminated film of: the first barrier insulating film serving as abarrier insulating film of the embedded copper wiring, formed on theinsulating film in which the copper wiring is embedded, and havingexcellent barrier properties to copper; and the second barrierinsulating film formed on the first barrier insulating film, and havingexcellent adhesiveness to a low dielectric constant material. Further,by forming such first and second barrier insulating films on the surfaceof the copper wiring, the TDDB life can be improved.

Also, the concentration of nitrogen in the barrier insulating film nearthe interface between the copper wiring and the barrier insulating filmis set higher than that of the barrier insulating film near theinterface between the low dielectric constant material film of the upperlayer barrier insulating film and the barrier insulating film, wherebythe reliability of the copper wirings can be improved. Furthermore, byforming such barrier insulating film on the surface of the copperwiring, the TDDB life can be improved.

Additionally, a film is formed by a copper compound (or metal other thancopper), whose diffusion coefficient is smaller than that of copper(Cu), and such a film is interposed between the copper film and thebarrier insulating film. Therefore, it is possible to further restrainthe diffusion of copper in the interface between the wiring and thebarrier insulating film and improve the stress migration characteristicsof the wiring and the like.

Furthermore, since the stress of the entirety of the laminated film(barrier insulating film) formed on the surface of the wiring iscontrolled so as to be −180 MPa or more, it is possible to restraintroubles arising from the stress migration.

The effects obtained by the representative ones among the inventionsdisclosed in this application will be briefly described as follows.

The reliability of the wirings, each of which includes the mainconductive film containing copper as a primary component, can beimproved.

Further, the reliability of the semiconductor devices can be improved.

1-14. (canceled)
 15. A semiconductor device comprising: a semiconductorsubstrate; a first insulating film formed over said semiconductorsubstrate; a wiring opening formed in said first insulating film; awiring having a first conductive film containing copper as a primarycomponent, and embedded in said wiring opening; a barrier insulatingfilm formed over said wiring and said first insulating film; and asecond insulating film formed over said barrier insulating film, andhaving a lower dielectric constant than that of an oxide silicon film;wherein a concentration of nitrogen in said barrier insulating film nearan interface between said wiring and said barrier insulating film ishigher than that of the said barrier insulating film near an interfacebetween said second insulating film and said barrier insulating film.16. The semiconductor device according to claim 15, wherein said barrierinsulating film is made of a material containing silicon, carbon, andnitrogen. 17-39. (canceled)